A digital television (DTV) signal (a transport stream multiplex of packets) is formed of multiple packets, some of which represent video data, some which represent audio data and some of which represent metadata. The metadata is used by a DTV receiver to reconstruct the packetized DTV signal for a given virtual channel. A terrestrial DTV broadcaster's bandwidth, or physical channel, can contain multiple virtual channels, where each channel can contain a program or some other content.
A DTV signal can conform to the Moving Picture Experts Group (MPEG) 2 standard. An MPEG2 Transport Stream is defined as a number of fixed-length packets. Each packet has a four-byte header that contains a synchronization byte, a packet identification number, a continuity count and several control bits.
The transport stream multiplex is a complex arrangement of separate, mostly-independent information. An MPEG2 transport stream multiplex can include up to 8192 different packet identifiers (PIDs). Typically, though, perhaps a dozen PIDs are used in a transport stream multiplex.
Analyzing or visualizing the contents of such a stream is difficult because the volume of data is large and the complexity of the data is relatively high. For example, a high definition television (HDTV) broadcast that complies with the American Television Standards Committee (ATSC), i.e., an ATSC-compliant HDTV broadcast, will minimally contain data that includes at least 10 separate packet identifiers (PIDs), and packets will be sent at a rate of approximately 2.4 million bytes of data, or 12.9 thousand packets, per second. And this merely represents a relatively simple transport stream. Streams with multiple standard digital television (SDTV) programs and full electronic program guide (EPG) support (another type of metadata) can include dozens of PIDs.
Understanding and visualizing such a great amount of data at even low rates can be very confusing.
The known monitoring systems provide a means of selecting specific packets based on PID and a pre-existing knowledge of packet location in the stream (packet occurrence). The display of these packets is done by providing a dump of the actual digital contents of a single packet along with some formatting to identify particular portions of the packet.
Some of the systems allow packets to be grouped and traversed based on the type of the packet as indicated by the PID. For example, the AT953-ATSC STREAM STATION model of monitoring and analyzing system available from SENCORE ELECTRONICS can do the following. Once a packet of a given type has been identified and its contents displayed, a user can click on a back button or a forward button to view the contents of the previous or next packet of the same type. But at any one instance, only the contents of a simple packet are displayed.
The known monitoring devices only characterize a packet by displaying its contents. That is, they fail to give a visual impression or characterization of the each packet in the transport stream multiplex independently of a display of its contents, especially as this relates to visually differentiating amongst the variety, and emphasizing the relative sequential arrangement, of different packets contained in the transport multiplex during a display of a portion of the multiplex. In addition, the user of the known monitoring devices must have extensive knowledge of the make-up of an MPEG2 stream in order to be able to select a packet whose contents are to be examined in more detail. For example, the user of the known monitoring/analysis systems can discover that the PID 49 is video by viewing the PAT, finding the associated PMT and then determining the type of PID 49 by looking at the detailed contents of the PMT.
In the computer industry, it is known to use a grid of color-coded boxes to depict the progress of a disk defragmenting operation. But such visual representations have never been applied to a transport stream multiplex. In more detail, as shown in FIG. 7, each box in the grid represents a cluster of data on the disk. As shown in FIG. 8, different colors are assigned to the boxes to denote whether a box corresponds to: data currently being read (prior to relocation by the defragmenting operation); data currently being written to a new, less-fragmented location; data having been relocated; free space; and data not yet operated upon in some way by the defragmenting operation. For the free space color, a first pattern (to denote data that will not be moved) or a second pattern (to denote a damaged disk area) can be superimposed. The boxes cannot be selected or clicked-on to retrieve additional information.